Lea Michele's life since boyfriend and Glee costar Cory Monteith died of a drug overdose has been fraught with unimaginable grief and heartache, says an insider. But that won't stop her from attending tomorrow's Teen Choice Awards.

"Every day is so hard. Just getting up in the morning means remembering that Cory is gone," a source close to Michele told People magazine. "It's incredibly painful."

Michele, 26, still plans to make her first public appearance at the Teen Choice Awards this Sunday night. The popular FOX comedy Glee has five nominations, and the whole cast has confirmed they'll be there for a special tribute to Monteith. Talk about a tear jerker.

Though she has been bravely soldiering on, Michele finds every minute difficult, according to the source. And who wouldn't? It's a wonder she's even been able to get out of bed each morning.

"It's a struggle," the friend said. "She's incredibly strong, but that doesn't make it easier."

Filming for Glee's fifth season started this past week and Michele is back on set -- which is pretty miraculous considering that it's been less than a month since Monteith's death.

Her 31-year-old boyfriend was found alone in a Canadian hotel room July 13. He died from a toxic mixture of heroin and alcohol after a night out with friends.

His ongoing battle with addiction came to light when he checked himself into rehab in the spring. But shortly before his death, he seemed to be doing better -- and there were even rumors that he and Michele planned to move in together and were close to getting engaged.

Monteith played the lovable Finn Hudson on the musical theater show, where Michele stars as Rachel Berry. His character will die in the season's third episode honoring him. Glee is scheduled to premiere a week later than originally planned Sept. 26 and go on an extended hiatus after the tribute episode to Cory.

In the meantime, all eyes will be on Michele and the rest of the cast at what is sure to be an emotional awards ceremony tomorrow night. My guess is that we will be even more impressed by Michele's strength and resolve through this tragedy than we are already.

Are you planning to watch the Teen Choice Awards and the tribute to Cory?